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Why Boston Suspension


bjbinsjo

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What are the product numbers for:

1. Front Gabrial Struts

2. Rear Manroe Rear Shocks.

What I am thinking is that the Struts and Shocks can be bought at any local supply house, very cheaply. There is enough information on this board to design the electronics to trick the computers.

Vince

1994 SLS

153,000 miles

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97 Cadillac STS Passive Strut Replacement

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Disclaimer: The procedure presented on this page documents how to install passive struts on a 97 Cadillac STS. I have not tried this on any other vehicle but mine. If this procedure works for you great, I assume no liability if it does not. Strut replacement can be a hazardous procedure, observe safety precautions when working on your vehicle.

Motivation: The Cadillac Seville STS equipped with the Northstar system employs the use of electronically controlled strut dampers. The system is called CVRSS and stands for Continuously Variable Road Sensing Suspension. In this system, the struts contain electronic actuators which vary the size of a valve within the strut to control its firmness. All 4 struts are linked to the system computer and are controlled independently; the system takes inputs from on board accelerometers and the ride height sensors. This system is supposed to give the driver the benefits of both a soft suspension and a firm suspension when needed.

However high tech the system is, the struts durability is no better than any other hydraulic strut. Many used Cadillacs are on the road now with failing or failed front struts. There are two failure modes, one electronic and the other mechanical. The front struts are more likely to fail as they bear the majority of the weight. It comes as a surprise to the owners of these cars when they ask the dealer or another shop for a swap and are told the cost is ~$800 per wheel. This inflated cost is due to the high price of the strut - an apparent $10-50 dollar device inserted into the base of the strut adds >$400 to the strut price.

This gives the owner 3 options: 1- ignore the problem and live with a bouncy and noisy ride, 2 - pay the money to get the replacement electronic struts and 3 - sell / trade-in your car. An option that seems too obvious has not been available, which is to substitute cheaper passive struts. The reason that this has not been an option is because without the electrical connection to the actuator the driver will get a "Service Ride Control" (SRC) message that cannot be removed by programming the DIC. Also, if you talk to a suspension shop or a dealer shop they will tell you that passive struts will mess with the ride height and level control system.

Not wanting to pay $800 on parts, I researched the CVRSS system and the potential to defeat the error messages. I was on a mission to put passive struts in my car.

CVRSS Facts: Through my web research and with the help of some online contacts, I found several interesting tidbits about the system.

1. There are two types of strut failure

a. Mechanical, the damping ability of the strut is reduced or non-existent, no SRC message present

b. Electrical, the actuator is damaged, constant or intermittent SRC message

2. Non strut related items may cause a SRC message, such as, position sensors

3. The struts respond to vertical acceleration of the vehicle. They have no feedback on their own performance.

4. All struts act independent of each other

5. The CVRSS system is responsible for electronic level control (rear struts only)

6. The system performs a diagnostic check on each strut every 16 seconds.

7. Strut actuators are controlled by a 2KHz pulse width modulated signal. With a 0% duty cycle, the struts are in a soft setting and at 100% are at firm.

8. Struts are not responsible for ride height.

9. Front struts do not affect electronic level control function

These facts are sufficient in telling us that we should be able to substitute passive struts with no ill effects, if the SRS message can be defeated. There is a lot more information regarding CVRSS online. Refer to the references if you are interested.

I performed an experiment to illustrate just how the CVRSS system controls the strut. I hooked a speaker in place of the strut actuator and turned the car on. I could hear a diagnostic pulse every 16 seconds. Bouncing the car you can hear a signal growing in strength. I did have some videos of this but were lost on a hard drive format. This is a good way to check to see if CVRSS control is functioning correctly.

Defeating the SRC: I found that a 10 - 12 ohm resistor will mimic the presense of the strut actuator and will trick the system into think that the electronic strut is still present. This was first tried by my associate Dan-O with no success. The reason being that on a 12 volt signal the resistor will dissipate up to 72 watts. A power resistor is needed. I use a 50 watt resistor on each side which works fine.

The resistor works because the diagnostic check is simply putting the 12 volt signal across the 2 signal lines while the system looks at the feedback voltage. The 12 ohm resistor plays the part of a resistor divider providing that correct feedback voltage. I have had the resistor in place for more than 2000 miles with no messages.

Parts and Installation: I will not go into great detail into how to install the struts since there are some great how-to's already online (see references). This will cover the parts, tools and tricks I learned to make the install easier.

Parts:

1. Struts - FE1 struts used by the 97 Deville and other E bodies will work. There are FE1 struts and FE7 struts available. I chose the FE1 struts

LF #22064723

RF #22064724

2. Power resistors - I bought 2, 12 ohm 50 watt power resistors from Digi-Key.

Digi-Key PN #TMC-50-12-ND

Tools:

1. Sockets - I used 10mm, 13mm, 15mm and 15/16" sockets for this job. The 15/16' will need to be a deep socket.

2. 15mm wrench

3. Vise grip

4. Standard screw driver

5. Wire stripper / cutter

6. Soldering iron

7. Marking tool - I used white-out

8. Torque wrench - up to 150 ft/lbs

9. Metal hammer

10. Impact wrench

11. Air hammer

12. Strut Spring Compressor

13. Zip ties

14. electrical tape

15. Utility lights

16. Jack

17. at least 2 jackstands

18. lug wrench

19. Metal cutting tool ( dremel may work)

I cannot emphasize the importance of air tools enough. They make the job a lot easier to perform. I rented a good pair of spring compressors at Checker (rentals are free for the first two days and $6/day thereafter.) Sears also carries a good set for about $45. Also handy is a protractor / level for maintaining good alignment. I bought a tool at Sears for $3. It has a magnetic edge that can hold onto the brake disk to establish the camber.

SteveJ has a great guide on how to actually install the struts. (DEAD)

I will not duplicate the installation instructions, because they are basically identical for the 97. The only real difference between the struts is that the Strut to knuckle bolt holes are in different locations.

The one great difficulty I did have in removing my struts was getting the stabilizer link bolt out of the strut. Dan-O suggested using an air hammer, but that alone did not allow me to get the bolts out. I resorted to cutting a wedge out of the strut bolt hole with my rotozip cutting wheel attachment.

Using the cutting tool, I cut two slots from the edge of the strut toward the bolt hole. Once I got close, I used the chisel attachment for the air hammer to knock out the metal. One the second strut, it was adequate to just cut the slots and bend the metal a little to get the bolt out. This method is not too difficult and can be done fairly quickly - it just hacks up the struts.

I also, cut the electrical connection to the strut actuator at the strut. Be careful to cut the right wire. The brake line and wheel speed sensor wires are in the same vicinity.

Once the old strut is out and the spring is on the new one, put the new one in.

Finally, connect the resistor on the remaining portion of wire and seal up the ends.

Results / Conclusion: Before installing the new struts, my ride was extremely bouncy at highway speeds. The front end rattled going over bumps. I was starting to lose the enjoyment of my ride. Upon removing the old struts (133K miles on them), I found that they were in poor condition offering little to no damping whatsoever. With the new struts the ride is smooth and quiet. I am happy with the replacement. My alignment is a little off as I had preformed the procedure improperly 2 weeks previous to the final install. I had ordered the wrong set of struts. With an alignment, my car will feel as good as new.

(update 1/19/2004) Its been a while since I updated this page. I am happy to report that the car rides as well as ever after the alignment. I have driven over 10K without errors. In all this has been a great fix.

I have noticed that there are several "industrious" sites/individuals selling kits out there to bypass the RSS system since I put this site up. Maybe I missed the chance to make a little money, but I would rather this information be free - there are already too many mechanics making money off of us caddy owners. The thing that troubles me is that they are selling it as if it is some high tech original idea.

References / Thanks: Several people helped me with this over at www.gmforums.com (most of these links are now dead)

Thanks:

Dan-O (CadillacDan on GMForums)

SteveJ (DEAD LINK)

Bela

www.gmforums.com

www.caddyinfo.com

www.alldatadiy.com

www.gmpartsdirect.com

www.digi-key.com

http://www.delphi.com/automotive/handling/

http://www.autoed.com/resources/sam...es.CM-Ch_08.pdf

Discussion thread (DEAD LINK)

Contact: maydog@hotmail.com

aol.exe

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Just an opinion - Boston Suspension provides an economical, packaged solution to the problem of bad struts. Yes - there are probably cheaper ways to achieve the same end. For those who are unwilling or unable to invest the time or effort needed to round up the parts and disable the message, Boston appears to provide a viable option.

I'll be getting new struts soon, and may go the Boston route. Or I may go the custom crafted route.

Options are always good, and for me it is nice to know that there is an economical, packaged solution available.

Its also good to know that there are others here who have devised solutions on their own and are willing to share the results of their efforts.

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  • 5 weeks later...

The parts Boston Suspension sells are Monroe or Gagriel parts. But these are altered in a machine shop to fit our applications, also needed are the hardware parts they give you with the kit to connect the sway bar links.I bought 2 kits from them and I am very happy over a year 1996 seville and my wife's 99 Deville. Both have full Boston kits and work perfect just like their feedback on E bay.

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The parts Boston sells, are not out of the box... then to you. They are altered and rewelded in a machine shop and hardware peices are also needed to facilitate the connection of the sway bar links. I guess if you had the knowhow to find the right strut and knew a machine shop that could alter the correct things that they alter it would work.
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I see that my website was quoted here, there is still a lot of discussion about replacement struts. My solution, uses actual AC delco parts designed to be used on this car, just no one will tell you that. It sounds as if the other vendors are altering existing product to get it to fit the application. My guess is that they do this so they can source a cheaper part and increase their profit.

I do suspect that the "kits" provided by these companies are not much different than my parts list , other than the struts and price. It is highly possible that I have been driving on a converted suspension longer than anyone.

I would suggest to anyone to first look for OEM parts to fit their application before going aftermarket. Just look at the parts list for a base devill or sls of that year, passive part numbers should be available.

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I see that my website was quoted here, there is still a lot of discussion about replacement struts. My solution, uses actual AC delco parts designed to be used on this car, just no one will tell you that. It sounds as if the other vendors are altering existing product to get it to fit the application. My guess is that they do this so they can source a cheaper part and increase their profit.

I do suspect that the "kits" provided by these companies are not much different than my parts list , other than the struts and price. It is highly possible that I have been driving on a converted suspension longer than anyone.

I would suggest to anyone to first look for OEM parts to fit their application before going aftermarket. Just look at the parts list for a base devill or sls of that year, passive part numbers should be available.

I am not sure who you are, you say your website, who are you, do you sell struts or are you giving a solution to aftermarket, im a little confused

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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maydog -> maydog.dyndns.org or maydog@hotmail.com, thats me.

All of the data Jhonnydone posted is from my website. I, with the help of several people from the now extinct gmforums, came up with the extremely simple way to bypass the CVRSS system message and found replacement struts for the STS. I recieve 1 or 2 emails a week in regards to passive strut replacement, I try to answer the inquiries as well as I can. It is my way of giving back to a community of enthusiasts who have aided me several times.

I am not selling anything, in fact arnott, boston, etc. did not have a product until I posted the bypass method. They have just taken information freely available and sold it as a package. In fact, I believe I may have been in correspondence with one individual from one of these compaines, who was communicating with me under the guise of a person trying to bypass the message on their own 94 seville.

All I am saying is that bypassing the electronics was the only marginally hard part to going with a passive system (earlier attempts had failed because the experimenters has simply forgotten to take power dissipation into account) and that struts built to original equipment specs are readily available.

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and that struts built to original equipment specs are readily available.

Can you elaborate on that statement? I need to replace the struts on my 96 Deville. I am not going to spend a minumun of $600 a strut. Can you tell me what my least expensive option is? Thanks for sharing your experience and knowledge! Mike

I am unable to get into your webside, it requires a password

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I looked for different vehicles on delco's website for passive struts for a 96, I cannot find any. But for a 95 the 580-2 ($170 for both struts, not bad eh) is available for an 95 deville, I do not know if the chassis is the same between a 95 deville and seville, but it is the same between a 97 deville and 97 seville.

I am not aware of any suspension changes between 95 and 96. I can tell you that I had originally tried the 580-2 on my 97 sts and nearly had one completely installed before I found that one bolt on the strut knuckle was moved. (cadillac switched to an aluminum steering knuckle in 97) . My suspicions would be that this part would fit a 96.

I would check the steering knuckle part numbers between the two vehicles ( 96 sts and 95 deville) before laying down any cash on parts, however.

Maybe someone else more knowledgable about the suspension layout over the years can chime in.

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Hey thanks for the idea. Then its just a matter of suppressing the error message, correct?

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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  • 4 weeks later...

Bruce,

My 92 SLS doesnt require any thing special to disable the Service Ride Control message.There is an override described in the manual.I would think it would be the same on the sts,but I am not 100% sure.My mechanic would not install anything but the AC/delco passives replacements.He says he wont put Monroes in any car,and sees no reason to buy them with a different name on them.The cost of the replacement was about $1000 with labor for all four corners.

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Yes there is an override bit on the sts. Unfortunately it seems to apply only to the DIC code. The CVRSS system can still send out the error and the DIC will still display it. I figure all that bit does is stop the DIC from querying the system itself. This is the case on my 97 at least.

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